When? NEVER!

You might get the main part done now, but there are other bits you'll
want to change sooner or later. A decent shift knob (the G50 ones are
crap). Remote central locking. ABS (stock on some Caravelles... not
mine, unfortunately). Power steering ;-)

To add to my huge list of modifications-to-do, I am thinking of
trashing the entire lot of halfassed locks & doorhandles, cutting the
doorskins and installing Hiace items. Especially that awful slider
mechanism!